This study has two goals. One of these goals is to see if a new genetic test can determine if participants are at risk of developing Mild Cognitive Impairment due to Alzheimer's Disease (MCI-AD) within the next five years. The other goal is to evaluate the study drug called pioglitazone. Pioglitazone is being tested to delay the onset of MCI-AD. This study will look at the effectiveness of pioglitazone in delaying the onset of MCI-AD in cognitively-normal people who are at high-risk of developing MCI-AD, as idenfitied by the biomarker in the non-Hispanic/Latino Caucasian participants. In addition, approximately 300 cognitively normal elderly participants will participate in a volumetric magnetic resonance imaging (vMRI) substudy at selected sites. In the vMRI substudy, high-risk participants will be randomized (5:4) to receive either pioglitazone or placebo.